Ask that question to a hunter or a farm kid and you’re bound to get some giggles. Bulling – cows mounting cows is hardly an unknown thing or even a buck in rut mounting another buck is hardly an unknown behavior.

Clearly in the animal kingdom sexual activity – often rooted in rituals about dominance is hardly an unknown behavior. But it’s also clearly sexual in nature involving testosterone and estrogen – and the sex organs, even if it’s not about bearing off-spring.

Sex can be problematic, especially if it’s casual and with multiple partners due to the close contact and exchange of bodily fluids it involves. There are good reasons besides accidental reproduction of life to be concerned with sex outside of the desire to create children. Sexually transmitted diseases are real and can have life long consequences. But I don’t think the evidence points to homosexuality as being unnatural.